1. Field of the Invention
This invention relates to an ink tank for supplying recording liquid carried in a liquid injection recording apparatus, and to a liquid injection recording apparatus provided with a carriage carrying a scanning recording head and the ink tank.
2. Related Background Art
Many of liquid injection recording apparatus of this type are of a form in which, as shown in U.S. Pat. No. 4,447,820, a removably mountable cartridge type tank for recording liquid is mounted in the body of the apparatus, and as such tank (hereinafter simply referred to the ink cartridge), use has generally been made of a flexible bag having recording liquid hermetically sealed therein and contained in a housing having a vent port. That is, the ink cartridge of the construction as described above has often been used to achieve the purpose of preventing evaporation of the hermetically sealed recording liquid and the purpose of keeping the recording liquid under the same degree of pressure as the atmospheric pressure for smooth supply of the recording liquid.
However, in the thus constructed ink cartridge, the construction of the bag is complicated and costly and moreover, the bag which is flexible is unexpectedly susceptible to vibration and shock, and this has sometimes adversely affected the containment and supply of the recording liquid. So, there has been proposed an ink cartridge of simple construction and low cost which instead of a flexible sealed bag and contains recording liquid directly in a housing. In order that the supply of recording liquid may be accomplished smoothly, such an ink cartridge has been provided with a vent port or provided with atmosphere-communicating means for keeping the recording liquid at the atmospheric pressure for example, by inserting into the ink cartridge a hollow needle connected to a tube communicating with the atmosphere.
Further, in such an ink cartridge, in order to prevent the recording liquid from evaporating through the atmosphere-communicating means, it has been proposed to provide as the atmosphere-communicating means an electro-magnetic valve adapted to be opened when the main switch for recording is closed, or a valve adapted to be opened and closed by a pressure difference. It has also been proposed to minimize the size of the vent port to thereby prevent evaporation of the recording liquid.
However, using an electromagnetic valve or the like to open and close the communication between the atmosphere and the recording liquid requires a large-scale construction and a high cost, and the provision of a valve adapted to be opened and closed by a pressure difference has led to the disadvantage that the opening-closing of the valve can be affected by a change in the ambient temperature or the like. Also, making the vent port smaller has led to the disadvantage that the vent port is liable to be readily clogged by dust such as paper powder and becomes unable to fully perform its function as an atmosphere-communicating means. Further, such a cartridge has also suffered from the disadvantage that the recording liquid is generally liable to spill through the atmosphere-communicating means and thereby contaminate the surroundings.